What are the characteristics that insurers generally seek in a loss exposure to make it insurable?

Pure, accidental from the insured's standpoint, definite and measurable, a large number of similar exposure units, not catastrophic, economically feasible

Speculative, intentional, indefinite and immeasurable, unique exposure units, potentially catastrophic, economically infeasible

Pure, accidental from the insured's standpoint, indefinite and immeasurable, unique exposure units, potentially catastrophic, economically infeasible

Speculative, accidental from the insured's standpoint, definite and measurable, unique exposure units, not catastrophic, economic infeasible